He forwarded a photo of 1,180.
Print shop, or a cab, I could not see the header.
He asked, how much GST is sitting inside this.
I said, if the rate is really 18, GST inside is 180.
Original is 1,000.
That is the clean example I use on every call.
I made him zoom the rate first
1,180 without a rate is just a total.
Could be 18.
Could be 5 with something else mixed.
Could be no GST, just a lucky number.
I asked him to find the percent on the line.
He found 18%.
Good.
Then I said open GST calculator.
Amount box, 1180.
GST rate, 18%.
What do you want, Amount already has GST.
Not Add.
Add will grow the 1,180.
We are splitting the 1,180.
This is an estimate, not an official figure.
What the result should show
Original amount, 1,000.00.
GST inside, 180.00.
Inclusive total, 1,180.00.
CGST + SGST split, 90.00 each.
If your screen does not say that, the mode is wrong, or the rate is wrong, or you typed 11800.
I have typed 11800.
Extra zero.
Dont laugh, you will do it on a phone.
I also typed 118.
Then GST inside looks tiny and he thinks the shop is saintly.
Look at Inclusive total.
It should repeat 1,180.
Why 180, not 212
He had already done 18 percent of 1,180.
That is 212.40.
He wanted to subtract that.
I said no.
1,180 is 118 percent of the base if GST is 18 on the base.
Base is 1,180 / 1.18.
Base is 1,000.
18 percent of 1,000 is 180.
212 is the school shortcut on the wrong number.
I walked it three times.
1,000 + 180 = 1,180.
9 + 9 = 18 on the split story, 90 + 90 = 180.
He said ok, but why did my friend get 212.
Because the friend treated 1,180 as exclusive.
Friend thought tax is extra on 1,180.
That would be Add mode.
Total with GST would be 1,392.40.
GST 212.40.
That is a real math, just not this bill.
This bill already had the tax inside.
Same digits, different job.
I wrote the longer method note as how to pull original amount out of 18 percent GST.
Read that if 1,180 is clear but 7,670 is not.
If the 1,180 is not 18 percent
Then 180 is a lie.
5 percent inclusive, 1,180 / 1.05 is about 1,123.81, GST about 56.19.
12 percent inclusive, 1,180 / 1.12 is about 1,053.57, GST about 126.43.
28 percent inclusive, 1,180 / 1.28 is 921.88, GST 258.12.
I dont memorise those.
I change the GST rate box.
If you dont know the rate, stop announcing 180 in the group chat.
Go read GST 5, 12 or 18, which rate when.
Or look at the invoice.
Looking at the invoice is faster.
Some 1,180 totals are two items.
One at 18, one at 5.
Then one extract on 1,180 at 18 is wrong.
Split the lines.
This tool is one amount, one rate.
I said that, he said the photo is blurry.
Then we dont have 180.
We have a guess.
I dont like guesses on reimbursement.
Boxes again, because he opened invoice GST by mistake
There is another tool, invoice GST.
That one wants goods value, discount percent, then rate.
It builds a bill.
It does not start from 1,180 inclusive.
For this photo, stay on GST calculator.
Amount.
Rate.
Mode.
Three fields.
Amount already has GST.
Calculate.
If he wanted discount first, that is a different article and a different page.
For a shop line of 10,000 with 10 percent off, I use invoice GST.
Not today.
Today is 1,180.
Office reimbursement, what I write on the form
Base 1,000.
GST 180.
Total 1,180.
If they want CGST SGST, 90 and 90.
If they want IGST, I still put 180 in one bucket if the bill says IGST 18.
I dont invent a state code.
I copy the bill.
If accounts wants the GSTIN of the shop, that is on the bill, not on this calculator.
This calculator does not store the bill.
It does not file.
It splits.
I also write, rate assumed 18 from the print.
If someone later finds it was 12, my 180 is trash.
I say that in the email.
People skip that sentence.
Then they ping me after three weeks.
I still have the screenshot of the three boxes.
Yearly I dont, wait, this is not tax.
Amount 1180, rate 18, extract.
That screenshot is my memory.
Tiny mistakes that break 180
Space, comma, extra digit.
Typing 1,180 with a character the box hates.
If the box looks empty, type 1180.
Indian commas are for reading.
The input wants a number.
Picking 18% then changing Amount and forgetting to hit Calculate again.
Old result sits there.
You think 180 is for the new total.
Hit Calculate every time.
Leaving last week's 28% in the rate.
Then 1,180 extract is not 180.
Picking Add, seeing 1,392, and telling the shop they overcharged.
Shop will stare at you.
You brought the wrong mode.
I did that once in a stationery shop.
I still think about it when I pass that road.
Why I like 1,180 as a teaching bill
Because you can do it without a phone, once you know divide by 1.18.
Because 1,000 and 180 are clean.
Because cousin remembers it.
Next time a 11,800 bill comes, he can smell that it is ten times 1,180.
Original 10,000.
GST 1,800.
If the bill is 11,801, maybe round-off.
Dont start a war over one rupee.
If the bill is 11,210, maybe it is not 18.
Maybe discount.
Maybe two rates.
Open the tool, dont invent.
The result card will show two decimals.
Your shop may print whole rupees.
Those two displays is allowed to differ by loose change.
Those two displays are allowed.
I keep doing the is/are thing.
Ignore it.
The 180 is the point.
If rate is really 18, GST inside 1,180 is 180.
Fill Amount, fill 18, pick Amount already has GST.
That is the whole call.
I told him to delete the 212 from his notes.
He said he already sent 212 to accounts.
I said send a second message.
Better a second message than a bounced claim.
One more 1,180, then I stop
A software seat came as 1,180 on the card.
Same three boxes.
Amount 1180.
GST rate 18%.
What do you want, Amount already has GST.
Original 1,000.
GST 180.
If the mail said plus GST, that card total might already be inclusive, or it might not.
I still look at the tax line.
If the tax line already says 180, I am done.
If the tax line says 212, they treated 1,180 as exclusive.
Then I do not extract.
Then I use Add mode only if I am building a quote, not reading this card.
Same digits, again, two jobs.
I make him say 1,180 divided by 1.18 before he closes the tab.
If he can say it, the 180 sticks.
If he cannot say it, he will send 212 again next month.