Every form works the same way

Whether you are adding a customer or raising an invoice, the form behaves the same way. This is that behaviour, once.

How a form is laid out

Tabs across the top split a long form into sections. Details is where you start; the others hold things you need less often.
A red Required mark beside a label means you cannot save without it.
A small circled i beside a label explains a field in one line when you hover over it. Worth doing on anything you are unsure about.
Buttons along the bottom. On documents this bar sticks to the bottom of the window so it is always reachable, however long the form is.

Fill it in and save it

Work through Details first — the rest of the form often depends on what you choose there.
Pick from a list rather than typing where you can. Start typing in a picker and it narrows as you go.
Check the other tabs if the form has them.
Click the save button at the bottom. Where a form has both a draft and a final option, see How documents work for which to use.

Saving keeps you on the form and confirms with a short message at the top of the screen. If it did not save, the reason appears in red beside the field that caused it.

Keyboard shortcuts

CtrlS saves.
CtrlShiftS saves and confirms, on documents that have both.
CtrlP opens the printable copy.
CtrlB goes back to the list without saving.

On a Mac these are the same shortcuts with the command key instead of Ctrl.

Pickers, and creating as you go

When a form asks for a customer, a stock item or an account, you get a picker rather than a plain box. Two things are worth knowing.

You can search inside it. Type a few letters of a name or code.
You can create the missing thing without leaving the form. Most pickers offer to add a new record inline, so a customer you have not set up yet does not force you to abandon a half-finished invoice.

When a form will not let you save

If nothing appears to happen when you save, it means a required field further up the form is empty. The page jumps to the first problem and marks it in red — scroll up if you landed mid-form.
If a field is greyed out, either it is filled in for you from something else, or the record has gone past the point where that field can change.
If leaving a page warns you about unsaved changes, it means exactly that. Cancel the warning and save, or leave and lose them.
If saving fails on a date, it means the date falls in a closed month. See Financial Periods.