Shop guy said the bag is 2,360, GST already in.
My cousin needed the base for a reimbursement form.
He subtracted 18 percent of 2,360 on his phone.
That is the wrong direction.
I told him, inclusive price divided by 1.18.
That is the whole trick.
He did the school percent the wrong way
18 percent of 2,360 is about 425.
He wrote original 1,935.
Looks neat.
It is wrong for an inclusive bill.
If the shop already stuffed GST into the sticker, the 18 percent sits on the base, not on the final.
Base times 1.18 equals the sticker.
So sticker divided by 1.18 equals the base.
2,360 / 1.18 is 2,000.
GST inside is 360.
His 425 was a different story.
I said, use the GST calculator so you dont fight the decimal on a bus.
This is an estimate, not an official figure.
Which boxes on this site
Amount.
That is the number you already have.
If the bill is inclusive, type the inclusive total.
GST rate.
Pick 18%.
Dont pick 18 if the invoice line says 5 or 12.
What do you want.
This is the mode.
Amount already has GST.
That is extract.
Add GST on this amount.
That is the other direction, when you have a clean quote and you want to slap tax on it.
For pulling original out, you want Amount already has GST.
Hit Calculate.
Original amount is the headline.
GST inside is the tax chunk.
Inclusive total repeats what you typed.
CGST + SGST split shows half and half.
For intra-state 18, people talk 9 and 9.
This box shows the full GST first, then that split.
I dont file returns from this split.
It is just a number split.
The 1,180 example I keep repeating
I always make him do 1,180.
Amount 1180.
Rate 18%.
Mode Amount already has GST.
Original comes 1,000.
GST inside 180.
Inclusive 1,180.
Half and half, 90 and 90.
If that does not appear, he picked Add by mistake.
Add on 1,180 at 18 percent gives a bigger total, about 1,392.
That is a different job.
I wrote a whole page on that 1,180 bill, bill is 1,180, how much GST is inside.
Same tool.
Same 180.
I repeat it because 1,180 is easy to check in your head.
1180 / 1.18 = 1000.
If your head cannot do 2360 / 1.18, the box can.
If the rate is not 18, the 1.18 trick is wrong.
5 percent inclusive is divide by 1.05.
12 is 1.12.
28 is 1.28.
I dont guess the rate from memory if money is big.
I look at the invoice HSN line.
If you are unsure which slab even applies, GST 5, 12 or 18, which rate when is the sister rant.
Why people subtract 18 percent anyway
Because school taught "find 18 percent of the number".
Nobody taught "the number is already 118 percent".
So they take 18 percent of the inclusive and subtract.
That understates the base and overstates the tax, or the other way around depending how they label it.
In the 2,360 case, he understated the base by 65 rupees.
On a reimbursement, accounts uncle will send it back.
On a shop margin sheet, you will think GST ate more than it did.
I have done this wrong on a cab bill too.
I was tired.
I subtracted 18 percent of the total.
The difference was small, I ignored it.
Next month a bigger bill, the difference was not small.
Now I force the extract mode.
Amount already has GST.
Rate from the bill.
Not from my mood.
Add mode, so you dont mix them
Sometimes cousin has a quote without tax.
Printer says 4,000 plus GST.
Then Amount is 4000.
Rate 18%.
What do you want, Add GST on this amount.
Total with GST 4,720.
Original 4,000.
GST 720.
That 720 is 18 percent of 4,000.
Correct, because the 4,000 was exclusive.
If he puts 4,000 in extract mode, the tool thinks 4,000 already has GST.
Original becomes about 3,389.
GST about 611.
Wrong story for that quote.
Mode is not decoration.
Mode is the job.
I say it like that on the call so he hears it.
The two jobs is different.
The two jobs are different.
Yes I mixed is/are.
He still understood.
Discount sitting under the GST
Some invoices cut discount first, then GST.
If you only have a grand total, extract mode on the grand total gives you a blended split.
It does not tell you the discount line.
For a shop invoice with a percent off, use the invoice tool, not only this GST box.
I walk that in GST after discount on a shop invoice.
If you extract 18 percent from a total that also has a round-off of one rupee, you may be off by loose change.
Billing software rounds.
This box shows two decimals.
Dont fight one rupee like it is a raid.
If the price never had GST, extract is nonsense.
A vegetable guy quoting 80 rupees is not hiding 18 percent inside unless his board says so.
Dont divide every sticker by 1.18.
You will invent a tax that was never there.
How I check the answer without trusting myself
Original times 1.18 should come back to the inclusive, maybe a paisa off.
GST should be inclusive minus original.
GST should also be original times 0.18.
If those three dont hug each other, I typed the wrong rate or the wrong mode.
I do this check on paper for 1,180 every time I teach someone.
1000 times 1.18 is 1180.
1000 times 0.18 is 180.
1180 minus 1000 is 180.
Done.
For 10,000 inclusive at 18, original is 10,000 / 1.18, about 8,474.58.
GST about 1,525.42.
I dont keep that in memory.
I keep 1,180 in memory.
Everything else, the box.
Indian commas on the result, 1,525.42 looks like money.
8,474.58 too.
If your form wants whole rupees, you round the way accounts asks.
I dont invent their round-off rule.
Small office stories, same math
Laptop bag 2,360, we already did.
A domain renewal 1,180, same 1,000 plus 180.
A furniture quote 47,200 inclusive, divide by 1.18, base 40,000, GST 7,200.
I did that one for him last Diwali.
He had typed 47,200 minus 18 percent, and the vendor laughed.
Vendor was right to laugh.
A hotel bill with 18 on rooms and 5 on food is not one extract.
Run once per rate.
Add the originals if you need a combined base.
This GST tool is one rate at a time.
Dont dump a mixed bill into one Amount and pick 18 for the whole thing.
That is how you lie to yourself.
If IGST is on the bill, the rate box is still the rate.
Split is a filing question.
This page is not GSTR.
I say that because someone always asks.
What I type, one more time, slow
Amount, the inclusive figure.
GST rate, 18% if the line is 18.
What do you want, Amount already has GST.
Calculate.
Read Original amount.
Read GST inside.
If you needed to add tax instead, change the mode.
If you needed 12 percent, change the rate.
If you needed discount then tax, leave this page.
Dont send me a screenshot of Add mode and ask why original looks like the number you typed.
In Add mode, original is what you typed.
In extract mode, original is the pulled-out base.
Two different headlines.
I hang up after he repeats 1180 divided by 1.18.
If he can say that, he can survive the reimbursement form.