El vencimiento sigue al periodo de facturación.

Yes, seguir often means to continue, but it can also mean to follow.

In this sentence, sigue a means comes after or follows:

• El vencimiento sigue al periodo de facturación.
• Literally: The due date follows the billing period.

So here sigue does not mean continues. It means comes next after.

Because seguir can take a direct object, and when that object is a masculine singular noun with el, Spanish combines a + el into al.

Here is the structure:

• seguir + a + el periodo
• a + el = al

So:

• sigue al periodo = follows the period

This a is part of the pattern used with seguir in this sense.

In Spanish, a + el always contracts to al.

So:

• a el periodo → al periodo

This is a standard contraction, just like:

• de + el → del

Examples:

• Voy al banco.
• Viene del trabajo.

Vencimiento usually means due date, expiration, or maturity, depending on context.

In billing or finance, it often refers to the date when a payment is due:

• fecha de vencimiento = due date

In this sentence, el vencimiento is best understood as the due date or the payment due date.

Spanish often drops words that are understood from context.

• la fecha de vencimiento = the due date
• el vencimiento can also mean the due date in billing/financial language

So el vencimiento is a shorter, more compact way to express the same idea when the context is clear.

Usually, yes.

• periodo de facturación = billing period
• In many practical contexts, it can also correspond to billing cycle

Facturación comes from facturar, which relates to billing/invoicing. So this phrase refers to the time span covered by billing.

Spanish often uses noun + de + noun where English might use a noun as an adjective.

So:

• periodo de facturación = literally period of billing
• Natural English: billing period

This structure is very common in Spanish:

• tarjeta de crédito = credit card
• centro de salud = health center
• fecha de pago = payment date

Because the subject is singular:

• El vencimiento = the due date

So the verb must also be singular:

• El vencimiento sigue...

If the subject were plural, the verb would change:

• Los vencimientos siguen al periodo de facturación.

The verb agrees with el vencimiento:

• el vencimiento = singular
• sigue = third-person singular

Also, semantically, the sentence is saying that the due date comes after the billing period. So el vencimiento is doing the action of following.

A learner might momentarily wonder whether periodo is the subject, but the verb placement and meaning make el vencimiento the subject.

Yes. A clearer everyday version might be:

• La fecha de vencimiento viene después del periodo de facturación.

That version may feel more transparent to learners because:

• la fecha de vencimiento is more explicit than el vencimiento
• viene después de is easier to understand than sigue a

But the original sentence is still perfectly valid, especially in formal, administrative, or billing-related language.

Both periodo and período are accepted forms.

In many places, periodo is common, while período is also seen and understood. This is one of those words where both spellings are considered valid.

So:

• periodo de facturación
• período de facturación

Both can be correct.

Not exactly.

• factura = bill, invoice
• facturación = billing, invoicing, or the billing process

So:

• periodo de facturación = billing period not
• invoice period

They are related words, but they are not interchangeable.

Yes. This is a common use.

Examples:

• El verano sigue a la primavera.
  Summer follows spring.

• La reunión sigue al almuerzo.
  The meeting follows lunch.

• Una pausa sigue a la presentación.
  A break follows the presentation.

So in your sentence, seguir a is being used to show sequence: one thing comes after another.