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Lesson 13 / 21 · Beginner

Reading a Lightning invoice

Understand amount, expiry and payment status.

10 MIN WITH PRACTICEREAD → TRY → REFLECTNO WALLET NEEDED

By the end, you’ll be able to…

  • Locate the important parts of a request.
  • Explain why an expired invoice needs care.
Your learning map

Three questions to carry into this lesson.

01Locate the important parts of a request.
02Explain why an expired invoice needs care.
Use these goals to guide your reading. Try the paper exercise, then explain the result in your own words.

The recipient makes a request

A Lightning invoice can encode an amount, payment hash, timestamp, expiry and descriptive information. BOLT 11 defines a widely used invoice format. Wallets present the encoded fields in a friendlier view. The text description is useful context, but it does not prove that the person sending the invoice is the artist or organizer you intended to pay.

Expiry is a condition, not a countdown game

A recipient may use an expiring invoice because its terms or receiving setup should not remain open indefinitely. Do not assume that an old screenshot remains payable. If a previous attempt has an uncertain status, resolve that attempt before obtaining and paying a new request. Otherwise two different requests might refer to one intended purchase.

The amount can be explicit or requested later

Some invoice workflows allow the payer to specify an amount; others already fix it. That difference changes what must be checked in the wallet. For a beginner, the safest classroom exercise is to annotate a mock request on paper. No real invoice or payment is needed. Distinguish invoice expiry, network routing and the status of an actual payment: they are separate pieces of information.

Your turn / A paper experiment

Practice on paper

An imaginary invoice for 8,000 sats expired before a learner opened it. No payment has been attempted. What information should a replacement preserve?

I’ve tried it — show the worked answer

The intended recipient, order purpose and agreed amount should remain clear, while expiry and technical invoice fields can change. Verify the replacement through the known recipient rather than editing encoded payment data yourself.

Want to explore with buttons and instant feedback? Try the practice lab ↗

Think it through

Make a choice. Discover why.

Choose an answer and check the explanation. You can retry as often as you like. These are practice questions, not a test of mastery; answers are not saved or sent.

1. Is the description cryptographic proof of a merchant’s identity?
  • Yes
  • No
Read the explanation

No. Check the recipient independently.

2. Should a pending attempt be ignored when asking for a new invoice?
  • Yes
  • No
Read the explanation

No. Resolve its result to avoid paying twice.

One idea to take with you

An invoice is a structured request; read its conditions.

Your learning, at your pace

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